Forecasters said the storm would likely stay below hurricane force until it reached the Gulf of Mexico on Sunday, and they shifted its projected track back eastward and it remained a possible threat to Tampa, Florida, where the Republican National Convention starts Monday.

Communications in Haiti are often spotty and there were no official reports any damage late Friday.

Government and international aid groups in Haiti's capital were prepared to evacuate several thousand people from settlement camps that sprang up in the aftermath of the 2010 earthquake. But the main threat appeared aimed at Les Cayes, a city of about 45,000 people on the southwestern coast that is prone to flooding during heavy rain.

Forecasters said Isaac could drop up to eight to 12 inches (20 to 30 centimeters) of rain on the island of Hispaniola, which is shared by Haiti and the Dominican Republic. Haiti is heavily deforested and just a few hours of steady rain can trigger deadly mudslides.

"That kind of rain is going to cause some life-threatening flash floods and mudslides," said Dennis Feltgen, a spokesman for the U.S. Hurricane Center in Miami.

Isaac was centered about 65 miles (100 kilometers) south-southwest of Port-au-Prince, the Haitian capital, late Friday, and its maximum sustained winds had increased to 70 mph (110 kph). It was moving west at 14 mph (22 kph). Tropical force winds extended nearly 200 miles (321 kilometers) from the storm's center.

Cuba declared a state of alert Friday for six eastern provinces, according to a Civil Defense announcement read on the afternoon news, and five central provinces were put on preliminary watch. Vacationers in tourist installations of those regions were evacuated.

Radio Baracoa, from the city of Baracoa on the northern coast of eastern Cuba, reported that high seas began topping the city's seawall Friday night. Reports said lower than normal rains had left reservoirs well below capacity and in good shape to absorb runoff.

Cuba has a highly organized civil defense system that goes door-to-door to enforce evacuations of at-risk areas, largely averting casualties from storms even when they cause major flooding and significant damage to crops.

Haitian Prime Minister Laurent Lamothe urged people to avoid crossing rivers and to stay calm, saying "panic creates more problems." He said the government had set aside about $50,000 in emergency funds and had buses and 32 boats on standby for evacuations.

About 400,000 people remain in settlement camps comprised of shacks and tarps in the wake of Haiti's devastating 2010 earthquake.

In Port-au-Prince, a city of some 3 million ringed by mountains, people went to work as usual Friday, but commercial banks closed at noon and some residents took precautions as the sky darkened, rain fell and the wind picked up.

"Just in case this gets very bad -- the sky is turning gray -- I'm making sure we have enough food in the house," said 25-year-old Joanne Dorville as she carried home rice, sardines, black beans and cooking oil that she had purchased in a street market.

Haitian authorities and aid workers from the International Organization for Migration and the Haitian Red Cross had planned to evacuate as many as 8,000 people from a tent camp at the edge of the capital but few accepted. Two school buses that were supposed to shuttle the people to temporary shelters drove away empty.

"If I leave for a shelter, by the time I come back, everything I have will be gone," said Charles Delizaire, a 39-year-old resident of the settlement named Marassa.

More than a hundred people were at a shelter in a school that President Michel Martelly toured along with Lamothe, the prime minister. Martelly greeted mothers and their children, but after the visit some people began to leave.

"They dragged me from the camp and brought me here," 38-year-old Marlene Charles, thirsty and hungry, said about the aid groups. "There's no way I'm going to spend the night here."

So far, Isaac itself had caused no reported injuries or deaths, but police in Puerto Rico said a 75-year-old woman died near the capital of San Juan on Wednesday when she fell off a balcony while preparing for the storm.

In the Dominican Republic, authorities evacuated people from low-lying areas but, as in Haiti, they encountered resistance. Still, authorities said they evacuated nearly 2,900 people. The majority were transferred to the homes of relatives while about 300 were sent to government shelters.

Flooding was reported in Santo Domingo and Santiago but no reports of injuries.

Organizers of next week's Republican National Convention in Tampa said they were working closely with state and federal authorities on monitoring storm as they prepared for the arrival of 70,000 delegates, journalists and protesters, and Florida Gov. Rick Scott said there were no plans to cancel the convention.

Out in the eastern Atlantic, former Tropical Storm Joyce degenerated into a weak low pressure system Friday.